Broken Windows

Broken Windows Theory [Wikipedia link] is the theory that there is a direct link between a community's level of disrepair, and it's crime rate. The theory posits that if people see a neighborhood in bad shape (e.g. broken windows everywhere) then they are more likely to commit a crime.

The current Chief of the LAPD, Charles Beck is a huge believer in Broken Windows Theory, and is actively implementing it in Los Angeles.

Recently a study was done by Kees Keizer in The Netherlands:

In six experiments in the Netherlands, Keizer observed and compared the behavior of people under artificial conditions of order and disorder. Invariably, he found that disorderly conditions encouraged further and more serious levels of disorderly behavior. In one experiment, for example, Keizer placed an envelope conspicuously containing five euros in a mailbox. When the mailbox was clean, 13% of people who passed it stole the money; when it was covered with graffiti, 27% took it.

-George L. Kelling [Forbes,link]

Here is the paper published by Keizer http://www.sciencemag.org/cgi/data/1161405/DC1/1